Identifying and appropriately demarcating subsurface nonpalpable lesions in tissue presents a number of difficulties for radiologists. Unless the lesion is properly localized, that is, limited or restricted to a definite area or region, the surgeon may remove an unnecessarily large amount of tissue or may inadvertently leave a portion or all of the lesion unexcised.
Nonpalpable breast masses are presently localized using a compression biopsy paddle. The biopsy paddle, such as incorporated in the Phillips Mammographic System available from Phillips, Netherlands, has a locator plate which is rigidly and permanently held by a bracket that in turn mounts to a support which permits the paddle to be raised and lowered. The locator plate has a number of access holes distributed across the plate and arranged in rows and columns. To localize a lesion, the breast is placed on a cassette containing X-ray film and positioned to place the lesion close to the upper surface. The biopsy paddle is lowered to compress the breast and the X-ray film is exposed by passing radiation through the locator plate, which is radiotranslucent.
The lesion is located on the film and the radiologist then must insert a localization needle through an access hole of the locator plate into the breast and into the lesion. However, the access holes are separated by intervals of solid material. When a small lesion lies beneath an interval rather than an access hole, the biopsy paddle must be elevated and the patient's breast physically moved either medially or laterally to attempt to bring the lesion beneath an access hole. Moving the patient physically over the cassette is difficult, especially if the patient is sweating, and moving the patient only a small amount is particularly difficult. Further, physically moving the breast further agitates an already apprehensive patient.
After adjustment of the breast the biopsy paddle is lowered to again compress the breast and another X-ray exposure is taken. If the lesion still does not sufficiently underlie one of the access holes, the cumbersome adjustment procedure must be repeated. Once the lesion is properly positioned relative to an access hole, the needle is inserted and another X-ray film is exposed to record the position of the needle relative to the lesion. Finally, after reorienting the breast 90.degree. and repositioning the biopsy paddle, an additional X-ray film exposure is taken perpendicular to the previous X-ray exposure to locate the needle in three dimensions relative to the lesion.
Contamination problems are also present in the above system. Since the locator plate is permanently attached to the surrounding bracket, the system is unsuited for gas sterilization. Truly effective sterilization of a plastic instrument is provided by exposure to ethylene oxide. After this exposure, the instrument must stand for at least seven days to insure that the toxic gas has fully left the paddle. Presently, the paddles are simply swabbed with alcohol. But blood, sweat and other bodily fluids which contact the plate are best neutralized through gas sterilization.